1. Field of the Invention
The present disclosure relates to an evaporation cycle heat exchange system for a vehicle. More particularly, it relates to an evaporation cycle heat exchange system for a vehicle, which is a new type of cooling system that cools vehicle electronic components, a fuel cell stack, an internal combustion engine, an automatic transmission, a turbocharger, etc. using an evaporative heat exchanger, thus improving cooling efficiency and reducing the size of components such as a radiator.
2. Description of Related Art
The temperature of combustion gas in a cylinder of an internal combustion engine typically ranges from 2,000 to 2,500° C., and most of the heat from the hot combustion gas is transferred to engine components such as the cylinder, cylinder head, piston, values, and the like.
When the temperature of the components excessively increases, the strength of the components is decreased to cause engine trouble, the durability of the engine is reduced, and the combustion conditions of the engine become worse, thus reducing the engine's power.
Moreover, when the engine is over-cooled, the amount of heat lost by the cooling is large, and thus the efficiency of the engine is reduced and the amount of fuel used is increased. Accordingly, a cooling system to maintain the temperature of the engine at about 80 to 90° C. is provided in the vehicle.
A hybrid vehicle is driven by an electric motor during cruising, during gentle driving, or during cruising at low and medium speed and driven by both the internal combustion engine and the electric motor during acceleration and during rapid acceleration.
Moreover, the hybrid vehicle is driven by the internal combustion engine during cruising at high speed, thus improving fuel efficiency.
Such a hybrid vehicle includes a cooling system consisting of an electronic component cooling system and an internal combustion engine cooling system.
A fuel cell vehicle is driven by a fuel cell in which hydrogen and oxygen are combined in a chemical reaction to produce electricity and water, and the produced electricity is used as a power source.
Such a fuel cell vehicle includes a cooling system for removing waste heat from a fuel cell stack. The cooling system for the fuel cell vehicle has a structure in which a coolant such as pure water or water is supplied to a radiator by operation of a pump such that the radiator radiates the heat of the coolant to the outside using a fan or traveling wind.
Since the cooling systems of most vehicles employ the radiator, which transfers heat from the coolant to the air, it is difficult to improve the cooling efficiency, and the size or capacity of the radiator is increased.
FIG. 1 is a schematic diagram showing a cooling system of a hybrid vehicle.
As shown in FIG. 1, the cooling system of the hybrid vehicle includes an electronic component cooling system and an internal combustion engine cooling system, each having a coolant circulation passage which will be described below.
The electrical component cooling system has a coolant circulation passage in which the coolant is circulated through an inverter 15>a reservoir 16>an integrated starter-generator 17>an electronic component radiator 18>a water pump 12>and the inverter 15, that is, through reservoir 16, and so on back through inverter 15.
The internal combustion engine cooling system has a coolant circulation passage in which the coolant is circulated through an internal combustion engine 10>an internal combustion engine radiator 11>a water pump 12>and the internal combustion engine 10.
Here, reference numeral 13 denotes a cooling fan, and reference numeral 14 denotes a cooling module.
The efficiency of the radiator in the hybrid vehicle is increased when the temperature difference between fluids to be heat-exchanged is larger, and a thermal head generally does not exceed 10° C.
In the case of the internal combustion engine radiator, the temperature at an inlet side ranges from 100 to 110° C. and the temperature of outside air ranges from 40 to 45° C., and thus the temperature difference between two fluids is 55 to 70° C., which exhibits a relatively high cooling efficiency.
However, in the case of the electronic component radiator, the temperature at an inlet side ranges from 60 to 65° C. and the temperature of outside air ranges from 40 to 45° C., and thus the temperature difference between two fluids is 15 to 25° C., which causes deterioration of the cooling efficiency. Therefore, in order to provide a high capacity and a thermal head of about 10° C., a large-sized electronic component radiator is required, and another heat exchanger may not be disposed in front of the electronic component radiator to reduce the temperature of the flowing air.
FIG. 2 is a schematic diagram showing a cooling system of a fuel cell vehicle.
As shown in FIG. 2, the cooling system of the fuel cell vehicle includes an electronic component cooling system and a fuel cell stack cooling system, each having a coolant circulation passage which will be described below.
The electrical component cooling system has a coolant circulation passage in which the coolant is circulated through an inverter 15>a reservoir 16>a drive motor 23>an electronic component radiator 18>a water pump 12>and the inverter 15.
The fuel cell stack cooling system has a coolant circulation passage in which the coolant is circulated through a fuel cell stack 19>a reservoir 16>a fuel cell stack radiator 20>a water pump 12>and the fuel cell stack 19.
Here, reference numeral 13 denotes a cooling fan, and reference numeral 14 denotes a cooling module.
In the case of the fuel cell stack radiator mounted in the fuel cell vehicle, the temperature at an inlet side ranges 75 to 85° C. and the temperature of outside air ranges 40 to 45° C., and thus the temperature difference between two fluids is 30 to 45° C., which causes deterioration of the cooling efficiency (Q=M′CpΔT). Therefore, in order to provide a thermal head of about 10° C., a large-sized fuel cell stack radiator is required, and another heat exchanger may not be disposed in front of the fuel cell stack radiator to reduce the temperature of the flowing air, thus increasing ΔT. However, in the case where the electronic component radiator and an air conditioner condenser are positioned in front of the fuel cell stack radiator, it is difficult to improve the cooling efficiency.
Accordingly, the capacity of the radiator is increased to approximately two times that of the existing internal combustion engine radiator, or a cooling fan for a 1 KW high voltage motor is used (the capacity of a conventional cooling fan for an internal combustion engine is less than 250 W).
FIG. 3 is a schematic diagram showing a cooling system of an internal combustion engine vehicle.
As shown in FIG. 3, the cooling system of the internal combustion engine vehicle has a coolant circulation passage in which the coolant is circulated through an internal combustion engine 10>an internal combustion engine radiator 11>a water pump>and the internal combustion engine 10, the radiator including a header, a tank, and a core. The coolant is heat-exchanged with outside air by operation of a cooling fan 13.
Here, reference numeral 14 denotes a cooling module.
In the case of the internal combustion engine radiator, the sizes of the header and tank are large, and thus a radiator having a thickness of 50 mm and a width of 47 mm is required to form the cooling module.
Meanwhile, in order to meet pedestrian safety regulations and testing criteria of the Research Council for Automobile Repairs (RCAR), which is an international organization that works towards reducing insurance costs by improving automotive damageability, it is necessary to reduce the size of the cooling module. However, it is impossible to reduce the thickness of the conventional radiator due to the structures of the header and tank, and if the size of the cooling module is reduced, it is difficult to ensure the cooling efficiency.
Moreover, a turbocharger intercooler radiator has the same problem as the internal combustion engine.
FIG. 4 is a schematic diagram showing a cooling system of a vehicle automatic transmission.
As shown in FIG. 4, an automatic transmission 21 disposed on one side of an internal combustion engine 10 has a cooling system in which a liquid oil is circulated between the automatic transmission 21 and a water cooling type automatic transmission oil cooler 22 mounted in an internal combustion engine radiator 11 to perform heat exchange.
During cold start, the automatic transmission oil and the coolant in the radiator 11 are over-cooled to the same temperature as the outside air.
During operation of the vehicle, the automatic transmission oil is moved to the water cooling type automatic transmission oil cooler 22 in the radiator 11 by the drive force of a converter of the automatic transmission 21 and heat-exchanged with the coolant in the radiator 11.
During cold start, the coolant in the radiator 11 is over-cooled and the automatic transmission oil is kept at the cooled state until heated coolant in the engine is introduced into the radiator 11 and heat-exchanged with the automatic transmission oil by operation of a thermostat.
When the automatic transmission oil is over-cooled, the oil viscosity is increased, and thus a larger drive force is required, which is very disadvantageous in view of fuel efficiency.
That is, the fuel efficiency of the automatic transmission at low temperature is lower than that at high temperature at which the oil viscosity is reduced.
To solve the above-described problems, research aimed at improving fuel efficiency by increasing the oil temperature at low temperature using a separate device that heats the oil has continues to progress.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.